Tris-HCl Buffer Solution Research Articles

Synthesis and biological application of a water-soluble fluorescent probe for Fe3+ based on sodium benzo[c]chromene-2-sulfonate

Four water-soluble sodium 8-carboxy-7-hydroxy-6-oxo-6H-benzo[c]chromene-2-sulfonates (2a-2d) were prepared and structurally characterized by 1H NMR, 13C NMR and HRMS-ESI spectra. The experimental results showed that 2a-2d were new water-soluble photoluminescent materials with strong photoluminescence property, large quantum yield and Stokes shift. In view of the high fluorescence quantum efficiency, 8-carboxy-7-hydroxy-3-methoxy-6-oxo-6H-benzo[c]chromene-2-sulfonate (2b, Ф = 0.74) was applied to the detection of Fe3+ in water solution. And probe 2b not only exhibited a naked-eye color change from colorless to pink, but also displayed highly selective ‘‘turn-off’’ probe for Fe3+ with detection limit of 1.72 umol/L in comparison to Na+, K+, Ag+, Ca2+, Cd2+, Co2+, Cu2+, Mg2+, Ni2+, Pb2+, Zn2+, Al3+ and Cr3+ cations in Tris-HCl buffer solution (pH 7.24). Futhermore, the binding stoichiometry of 2b with Fe3+ was determined to be 1:1 by Job’s plot. Because of the good water-solubility and strong fluorescence in physiological pH, 2b was applied in monitoring intracellular Fe3+ of living Ramos cells successfully.

The interaction of light-activatable 2-thioxanthone thioacetic acid with ct-DNA and its cytotoxic activity: Novel theranostic agent.

In this study, a thioxanthone derivative, 2-Thioxanthone Thioacetic Acid (TXSCH2COOH) was used to analyze the type of binding to calf thymus DNA in a physiological buffer (Tris-HCl buffer solution, pH:7.0). Several spectroscopic techniques were employed including UV-Vis absorption and fluorescence emission spectroscopy and viscosity measurements were also used to clarify the binding mode of TXSCH2COOH to ct-DNA. The intrinsic binding constant Kb of TXSCH2COOH-ct-DNA was found as 2.5×103 M-1 from the absorption studies. Increasing of fluorescence emission intensity was found approximately 74.4% by adding ct-DNA to the TXSCH2COOH solution. Fluorescence microscopy was employed to display imaging of the TXSCH2COOH-ct-DNA solution. Increasing of the iodide quenching effect was observed when TXSCH2COOH was added to the double stranded DNA and the calculated quenching constants of TXSCH2COOH and TXSCH2COOH-ct-DNA were found to be 1.89×103 M-1 and 1.19×104 M-1, respectively. Additionally, the iodide quenching experiment was conducted with single stranded DNA which led to a high Ksv value. All the experimental results including the viscosity values of ct-DNA with TXSCH2COOH demonstrated that the binding of TXSCH2COOH to ct-DNA was most likely groove binding. Furthermore, TXSCH2COOH was found to be an A-T rich minor groove binder. This was confirmed by the displacement assays with Hoechst 33258 compared to Ethidium Bromide. The in vitro cytotoxic activity measurements were performed by MTT assay on HT29 cell line for 72h. TXSCH2COOH exhibited notable cytotoxic activities compared to the standard chemotherapy drugs, fluorouracil (5-FU), cisplatin in tumorigenic HT29 cell line. The 50% growth-inhibitory concentration (IC50) for TXSCH2COOH was 19,8μg/mL while 5-FU and cisplatin were 28.9μg/mL, 20μg/mL, respectively. The increase in cytotoxic effect when TXSCH2COOH is activated by light indicates the potential of being theranostic cancer drug candidate.

Monitoring of the Respiratory Activity of Cells Using a Microdevice with Microfabricated Clark-Type Oxygen Electrode

Introduction With the progress of cell engineering and the increase in the necessity to understand status of human body, measurement of the respiratory activity of animal and microbial cells in solutions of small volumes is required in many situations. In this trend, we have also developed a device with integrated Clark-type oxygen electrode to measure the antibacterial activity of neutrophils [1][2]. Although obtained results demonstrated the utility of the device, preparation and handling of the device needed expertise to obtain stable current output by avoiding unintended introduction of small bubbles into the electrolyte solution that influence the output current of the oxygen electrode. In addition, evaporation of water limited the lifespan of the oxygen electrode.To solve the problems, we propose a novel oxygen electrode structure. The structure including the cathode and anode, an electrolyte layer, and an oxygen-permeable membrane were completed in a dry state. Prior to use, water necessary for the reduction of oxygen was introduced into the electrolyte layer in the form of water vapor through the oxygen permeable membrane by simply immersing the chip in water, which remarkably simplified handling by end-users. In addition, we used sorbitol in the electrolyte solution to suppress the evaporation of water. We employed the device to monitor the respiratory activity of E.coli. Furthermore, the device was used to measure the antibiotic resistance of bacteria. Method Figure 1 shows the structure of the device. The oxygen electrode consisted of a platinum cathode (diameter: 1 mm) and Ag/AgCl anode formed on a glass substrate, a reservoir to accommodate an electrolyte solution, a circular paper to impregnate the electrolyte solution, and a silicone rubber oxygen-permeable membrane. Electrode patterns were formed by sputtering and lift-off. Platinum patterns were formed for the cathode and the base layer of the anode with a chromium intermediate layer. Silver patterns was additionally formed only on the anode area. A polyimide insulating layer was formed to delineate the active areas of the electrodes. The reservoir for an electrolyte solution was formed with SU-8 (Kayaku Advanced Materials). A circular paper (diameter: 3 mm) immersed in pure water was moved onto the cathode and anode in the SU-8 reservoir. Following this, 2 μL of 2% PVP solution was poured onto the paper. The solution was prepared with 1.0 M Tris-HCl buffer solution (pH 8.3) containing 1.0 M KCl, 4.0wt% sorbitol. After drying the electrolyte layer at ~30%RH for an hour, a silicone adhesive (KE-3475-T, Shin-Etsu Chemical) was spin-coated to form the oxygen-permeable membrane (thickness: ~100 μm). The oxygen electrode was activated by introducing water into the electrolyte layer through the oxygen permeable membrane in the form of vapor by immersing the entire chip in pure water. To measure the respiratory activity of cells, a PMMA chamber was formed and was tightly fixed on the oxygen electrode.In operating the device, -0.8 V was applied to the cathode with respect to the anode using an Autolab PGSTAT 128N potentiostat (Metrohm Autolab, Netherlands). The response of the oxygen electrode was checked by immersing the active area into air-saturated pure water and removing dissolved oxygen by adding Na2SO3. To measure the respiratory activity of E. coli, freeze-dried E.coli was activated by resuspending it in PBS containing 100 mM glucose. Solutions of different cell densities were prepared. The solutions were injected into the sample chamber, and the respiratory activity of E. coli was measured. Evaluation of the antibiotics resistance was performed using 1×107 CFU/mL E. coli suspension including 5 mg/mL piperacillin sodium salt. Results and Conclusions The output current was stabilized after 8 - 12 h of activation (Figure 2). Figure 3 shows the response curve of the oxygen electrode. The output current in air saturated water was stable, and the current decreased clearly when the dissolved oxygen was removed by adding Na2SO3. The 90% response time was 30 s. Figure 5 shows that glucose enhances the respiratory activity of E. coli at glucose concentrations higher than 100 mM. Figure 6 shows the current decrease depended on the density of E. coli and was significant in the range of E. coli density higher than 106 CFU/mL. The current decrease is directly correlated with oxygen consumption by E. coli., which also reflects the number of living E. coli. Figure 7 shows the response curves obtained with E. coli suspension containing piperacillin. In the presence of the antibiotics, current decrease was suppressed compared with the case without the antibiotics, demonstrating that the device can also be used for the determination of the minimum inhibitory concentration of antibiotics.

Fe3+-Sensitive Carbon Dots for Detection of Fe3+ in Aqueous Solution and Intracellular Imaging of Fe3+ Inside Fungal Cells.

In this article, the Fe3+-sensitive carbon dots were obtained by means of a microwave-assisted method using glutamic acid and ethylenediamine as reactants. The carbon dots exhibited selective response to Fe3+ ions in aqueous solution with a turn-off mode, and a good linear relationship was found between (F0-F)/F0 and the concentration of Fe3+ in the range of 8–80 μM. As a result, the as-synthesized carbon dots can be developed as a fluorescent chemosensor for Fe3+ in aqueous solution. Moreover, the carbon dots can be applied as a fluorescent agent for fungal bioimaging since the fungal cells stained by the carbon dots were brightly illuminated on a confocal microscopy excited at 405 nm. Furthermore, an increase in the concentration of intracellular Fe3+ could result in fluorescence quenching of the carbon dots in the fungal cells when incubated in the Tris-HCl buffer solution containing Fe3+. However, due to EDTA might hinder Fe(III) to enter the fungal cells, incubation in Fe(III)-EDTA complex solution exerted negligible effect on the fluorescence of fungal cells labeled by the carbon dots. Therefore, the carbon dots can serve as a potential probe for intracellular imaging of Fe3+ inside fungal cells.

Effect of T-ZnOw addition on the degradability of sol-gel derived SiO2-CaO-P2O5 glass-ceramics

The effect of tetra-needle-like ZnO whisker (T-ZnOw) addition on the degradability of sol-gel derived SiO2CaO-P2O5 glass-ceramics (58S glass-ceramics) was explored. The degradability of the prepared glass-ceramics was evaluated by immersing in simulated body fluid (SBF) and in Tris–HCl buffer solution for 1, 3, 7 and 14 days respectively. The degradability and biological properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR) and inductively coupled plasma (ICP). The results revealed that T-ZnOw addition has significant influence on the degradability and biological properties of the sol-gel derived 58S glass-ceramics. The 58S glass-ceramics doped with no more than 2.5 wt% T-ZnOw still have good biological activity. Furthermore, the degradability of the 58S bioactive glass-ceramics can be effectively reduced by the T-ZnOw incorporation. The conclusions indicate that it is feasible to tune the degradation rate of the material by T-ZnOw.

Modified EDTA selectively recognized Cu2+ and its application in the disaggregation of β-amyloid-Cu (II)/Zn (II) aggregates

The accumulation of the β-amyloid (Aβ) aggregates induced by Cu2+/Zn2+ in conjunction with toxicity is closely related to Alzheimer's disease (AD). Herein, we intended to improve the efficiency and selectivity of traditional chelator ethylenediaminetetraacetic acid (EDTA) combined with a fluorescent group 4-aminosalicylic acid (4-ASA)to acquire a novel potential chelator 4,4′-((2,2′-(ethane-1,2-diylbis((carboxymethyl)azanediyl))bis(acetyl))bis(azanediyl))bis(2-hydroxybenzoic acid) (EDTA-ASA) capable of disaggregating Aβ-Cu(II)/ Zn(II) aggregates. EDTA-ASA combines 4-ASA as fluorophore and multidentate amino nitrogen, hydroxyl and carboxyl groups to chelate Cu2+ from Aβ-Cu (II) aggregates. The specific selectivity of EDTA-ASA towards Cu2+ in Tris-HCl buffer solution was investigated by fluorescence measurements. It exhibits high recognition towards Cu2+ with no significant interference of other competitive metal ions, which overcomes the deficiencies of EDTA. Importantly, the binding sites and binding mode for Cu2+ were clarified through DFT calculations. The thioflavin-T (ThT) fluorescence analyses and transmission electron microscopy (TEM) results have revealed EDTA-ASA exhibited an enhanced disaggregation capability on Aβ-Cu (II)/Zn (II) aggregates in comparison to EDTA. The Cu2+ chelating affinity was sufficient for EDTA-ASA to sequester Cu2+ from Aβ-Cu (II) aggregates.

Ether based flexible bis Schiff base fluorescent colorimetric chemosensors for selective and sensitive detection of HF2− ion

Two simple and low cost bis Schiff base fluorescent colorimetric chemosensors L1 and L2 have been designed and synthesized. These sensors could detect important anion HF2− by change in both absorption and fluorescence intensity in methanol tris HCl buffer (1:1 v/v) solution at physiological pH. The mechanism of selectivity and sensitivity of these receptors to HF2− has proposed to be on the basis of photo-induced electron transfer (PET), chelation enhanced fluoresence (CHEF) and hydrogen bonding mechanism, confirmed by FT-IR, 1H-NMR and ESI-mass spectra. Interestingly, chelation of HF2− to the receptors takes place in 1:2 ratio, which has been confirmed by job plots analysis, ESI-mass spectra, DFT and TD-DFT studies. The detection limits of the probes L1 and L2 for HF2− were determined to be 6.1 μM for L1 and 3.94 μM for L2 respectively, on the basis of 3σ/K. Importantly, the low detection limits of L1 and L2 for HF2−suggest that L1 and L2 are sensitive sensors for detection of these ions in drinking water. The receptors L1 and L2 can successfully applied for detection and quantification of HF2− in real samples. To the best of our knowledge this is the third report of fluorescent colorimetric chemosensors for HF2− ions.

Fluorescent norbornene for sequential detection of mercury and biothiols

A pyrene functionalized norbornene (1) and its homopolymer (P1), which was obtained by the ring opening metathesis polymerization (ROMP) method, have been designed and synthesized. Both 1 and P1 exhibit fluorescence ratiometric sensing of Hg2+ ions in Tris-HCl buffer solution. In addition, the in situ obtained Hg(II) complexes 1-Hg2+ and P1–Hg2+ can sequentially detect biothiols, including cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) via restoration their original fluorescence. In addition, probe 1 has been successfully used for detection of Hg2+ and Cys in living cells.

Abstract P2033: Rationale For A Novel Approach To Hypertension Treatment Based On Immuno-neutralization Of Angiotensin-(1-12) Catalytic Sites With A Polyclonal Antibody

The biochemical pathways for the formation of biological active angiotensins continues to undergo significant revision with the demonstration of angiotensin-(1-12) as an endogenous substrate forming angiotensin II (Ang II) by a non-renin dependent mechanism. Research done in our laboratory established that Ang II generation from Ang-(1-12) is primarily mediated by ACE in the circulation and by chymase in cardiac tissues. In this study, we have utilized an antigen-antibody binding approach to block the cleavage sites of human Ang-(1-12) peptide with an anti-Ang-(1-12) polyclonal antibody (pAb) as a potential therapeutic strategy to prevent the catalytic action of chymase and ACE enzymes to generate Ang II. The pAb was generated against the C-terminus of the human Ang-(1-12) peptide sequence and its specificity for human Ang-(1-12) and cross-reactivity with other angiotensin peptides were determined in competitive binding assays. To block the cleavage sites, the radiolabeled human Ang-(1-12) [ 125 I-Ang-(1-12)] substrate was first neutralized by pre-incubating with or without anti-Ang-(1-12) pAb and then re-incubated with human recombinant chymase (hrChymase, 0.325 μg/mL) or 10 μL of rat serum (for ACE) in 50 mM Tris-HCl buffer solution containing 150 mM NaCl (pH 8.0) for 30 min at 37 o C. The reaction was stopped by adding an equal volume of 1% phosphoric acid and 125 I-Ang metabolic products were quantified by HPLC connected to an in-line flow-through gamma detector. Anti-Ang-(1-12) pAb showed high specificity for the human Ang-(1-12) sequence (EC 50 = 29.6 ng/mL) and negligible cross-reactivity with closely related angiotensin peptides. The non-neutralized human 125 I-Ang-(1-12) substrate was rapidly metabolized by both hrChymase and rat serum ACE to 125 I-Ang II (81% and 35%, respectively). In contrast, generation of 125 I-Ang II from neutralized 125 I-Ang-(1-12) substrate by either hrChymase or ACE was only 17% and 7%, respectively. The effective and potent blockade of Ang II generation from either chymase or ACE by combining Ang-(1-12) with an anti-Ang-(1-12) pAb now paves the way to develop new therapeutic approaches to hypertension treatment using Ang-(1-12) antibodies directed against the human sequence of this Ang II-forming substrate.

In vitro studies of α-TCP and β-TCP produced from Clinocardium ciliatum seashells

In this study, α-TCP and β-TCP were successfully produced via a mechanochemical method from aragonite structures, Clinocardium ciliatum seashells, at 850 °C, 1000 °C, and 1200 °C sintering temperatures. The characterization of the obtained materials was carried out via FT-IR, SEM/EDX, BET, XRD, ICP-OES analysis. Samples were soaked for 21 days in simulated body fluid (SBF) for a bioactivity test. Additionally, MTT assay was applied to determine the cell viability of samples. Bioactivity in vitro tests showed that bone-like hydroxyapatite formed when the α-TCP and β-TCP were soaked in SBF. TCP bioceramics had a noncytotoxicity effect on SAOS-2 osteoblast-like cells and cell viability increased in 1 to 7 days. The produced bioceramics have ideal pore sizes and properties that are suitable for supporting biological activities. Tris-HCl buffer solution was used to obtain the level of biodegradation. It was seen that α-TCP exhibited better dissolution features than β-TCP.

Noncovalent interactions of bovine trypsin with curcumin and effect on stability, structure, and function

The structural studies of trypsin with curcumin in Tris-hydrochloride (Tris-HCl) buffer solution (pH 8.0) was explored by UV–vis spectroscopic and fluorescence quenching method, kinetic reaction, circular dichroism (CD), Thermal denaturation, molecular docking, and molecular dynamic simulation. The curcumin could decrease trypsin absorbance. It was showed that curcumin could quench the fluorescence of trypsin by static quenching mechanism. This is in agreement with UV–vis results and CD studies in which the α-helix becomes more, and β-sheet becomes less than trypsin without ligand. The binding constant, the number of binding sites and thermodynamic parameters (ΔH°, ΔS°, and ΔG°) at two temperatures were calculated. The hydrogen bond and Van der Waals interaction were found as the main forces, which is in congruence with docking results. The outcome of the kinetic reaction indicates an uncompetitive inhibition by curcumin on trypsin. Molecular Dynamic simulation and Thermal denaturation results demonstrate that curcumin makes trypsin unstable and more flexible.

Mast Cell Peptidases (Carboxypeptidase A and Chymase)‐Mediated Hydrolysis of Human Angiotensin‐(1‐12)

IntroductionAngiotensin processing peptidases [carboxypeptidase A (CPA) and chymase] are stored in cardiac mast cell secretory granules and are co‐released into the extracellular environment after activation/degranulation. In the human heart, we showed that chymase is primarily responsible for angiotensin II (Ang II) generation from the alternate substrate angiotensin‐(1‐12) [Ang‐(1‐12)], which is present in human heart. In this study, we investigated whether there are any synergistic effects of CPA and chymase in the processing of Ang‐(1‐12).MethodRadiolabeled human Ang‐(1‐12) [125I‐Ang‐(1‐12)] substrate was incubated with CPA alone (0.325 μg/mL), human recombinant chymase (hrChymase) (0.325 μg/mL) or a combination of CPA + hrChymase (1:1 or 1: ⅓ ratio) in 50 mM Tris‐HCl buffer solution containing 150 mM NaCl (pH 8.0) for 0–15 min at 37 °C. The reaction was stopped by adding an equal volume of 1% phosphoric acid and injected on a C18 column. Eluted 125I‐Ang‐(1‐12) metabolic products were quantified by HPLC connected to in‐line flow‐through gamma detector. To determine the Km and Vmax, CPA and hrChymase were incubated with increasing concentrations (0–300 μM) of human Ang‐(1‐12) substrate for 20 min at 37 °C. The Km and Vmax were calculated using the Michaelis‐Menten equation.ResultsWe found that after 15 min of incubation, CPA sequentially metabolized Ang‐(1‐12) substrate into angiotensin‐(1‐9) [Ang‐(1‐9), 53% (major product)], Ang II (22%) and angiotensin‐(1‐7) [Ang‐(1‐7), 11%]. No further hydrolysis of Ang‐(1‐7) was detected during CPA incubation. In the presence of hrChymase alone, 125I‐Ang‐(1‐12) was directly metabolized into Ang II (89%) and no further hydrolysis of Ang II was detected. In the presence of both CPA + hrChymase (1:1 ratio), the amount of Ang II formation was 68% from 125I‐Ang‐(1‐12) within a 5 min incubation period. The formation of Ang‐(1‐9) and Ang‐(1‐7) were only 11% and 10%, respectively. When CPA + hrChymase were added in 1: ⅓ ratio for 5 min, the Ang II, Ang‐(1‐9) and Ang‐(1‐7) formations were 65%, 27%, 6%, respectively. The Km and Vmax values were 150 ± 5 μM and 384 ± 23 nM/min/mg of CPA and 40 ± 9 μM and 116 ± 20 nM/min/mg of hrChymase.ConclusionsThese findings suggest that compared to CPA, chymase shows a much higher affinity to metabolize Ang‐(1‐12) into Ang II. In addition, Ang II and Ang‐(1‐7) are the end products of chymase and CPA, respectively. Overall, our findings suggest that chymase, rather than CPA, is primarily responsible for Ang II generation from Ang‐(1‐12).Support or Funding InformationThis work was supported by grant from the National Heart, Lung and Blood Institute of the National Institutes of Health (P01 HL‐051952).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Smartphone colorimetric detection of calcium and magnesium in water samples using a flow injection system

Water hardness has implications for both human health and industry. The main components that make water hard are calcium and magnesium. The magnesium in hard water may provide a moderate health benefit, but calcium can cause serious problems in industrial processes. This paper presents a rapid-response, reliable and convenient device developed to measure calcium and magnesium ion concentrations continuously in water samples by using a smartphone analysis of colorness change. The ion detection is based on phase extraction equilibria in a specific ion-exchange substance membrane that contains an ionophore (selectively binding to specific ions), a chromoionophore (a lipophilic pH indicator), an ionic salt (a cation exchanger), a polymer (PVC) and a plasticizer. The device is built on a PDMS fluidic layer with six parallel detection chambers that allows the water samples to flow through at a specific rate to these chambers. An Android smartphone App was developed to acquire the color images after the ions exchange across the membrane, and the analysis of target ion concentration can be realized by the pre-loaded calibration curves. The results show that the colorimetric sensor is capable of determining Ca2+ concentration in an acetate buffer solution (pH = 5.3) and total hardness in a Tris-HCl buffer solution (pH = 7.2), covering the range of normal water hardness (from soft to very hard). The measurements on real samples were analyzed by both Image J and the App and were compared with results from a commercial hardness kit and inductively coupled plasma mass spectrometry (ICP-MS), demonstrating the accuracy and precision of our colorimetric sensor compared to a commercial sensor. This cost-effective device and automatic analytical smartphone app can be combined easily as a ready-to-go sensor for monitoring Ca2+ and Mg2+ continuously and simultaneously, which is convenient for use in resource-limited areas.

Superior fouling resistant PVDF membrane with enhanced filtration performance fabricated by combined blending and the self-polymerization approach of dopamine

This work presents a new and simple modification approach to fabricate a Polyvinylidene Fluoride membrane with superior permeation, separation, and antifouling performance. Dopamine was introduced by blending into the membrane casting solution and the membrane was prepared using a classic non-solvent induced phase separation technique. The prepared flat-sheet membrane was then dipped into a Tris-HCl buffer solution with a pH of 8.5 to trigger the polymerization of dopamine into polydopamine. The effects of the modification on the membrane characteristics were analyzed in terms of a change in the chemical components, hydrophilicity, surface porosity, and mechanical strength. In addition, the permeation, separation, and fouling resistant performance were studied by means of a filtration experiment using deionized water and humic acid solution as feeds. The results revealed that the addition of dopamine successfully increased the porosity by 300%, hydrophilicity by 180%, and water flux performance by 600% compared to the original membrane. Polymerization of dopamine into the polydopamine layer recovered the loss of rejection due to pore enlargement by dopamine blending from 91 to 93%. In addition, the blended and polymerized membrane successfully recovered up to 92% of pure water flux after backwash, which indicates the superior antifouling performance. It can be concluded that this new technique can be a potential approach to produce membranes for the water treatment process with overall excellent performance.

A specific fluorescent probe for fast detection and cellular imaging of cysteine based on a water-soluble conjugated polymer combined with copper(II)

In pure water system, the specific and rapid detection of cysteine (Cys) is very important and challenging. Herein, a new optical probe was developed for the purpose based on the complex of cupric ion (Cu2+) with a water-soluble conjugated polymer, poly[3-(3-N,N-diacetateaminopropoxy)-4-methyl thiophene disodium salts] (PTCO2). The fluorescence of PTCO2 in 100% aqueous solution can almost completely extinguished by Cu2+ ions due to its intrinsic paramagnetic properties. Among various amino acids, only Cys causes immediately the efficient recovery of the Cu2+-quenched fluorescence of PTCO2 with ~31-folds fluorescence enhancement because of the stronger affinity of Cys to Cu2+ leading to the formation of Cu2+-Cys complex through Cu-S bond and separation of Cu2+ from weak-fluorescent PTCO2-Cu(II) ensemble and thereby restoring the free PTCO2 fluorescence. In tris-HCl buffer solution (2 mM, pH 7.4), the intensity of the restored fluorescence is linear with the concentration of Cys, ranging from 0 to 120 μM and the estimated detection limit of Cys is 3.3 × 10−7 M with the correlation coefficient R = 0.9981. In addition, the PTCO2-Cu(II) ensemble probe exhibits low cytotoxicity and good membrane penetration, and its application in living cell imaging of Cys has also been explored.

Hierarchical Au nanoclusters electrodeposited on amine-terminated ITO glass as a SERS-active substrate for the reliable and sensitive detection of serotonin in a Tris-HCl buffer solution.

Although serotonin (5-HT) is one of the most important neurotransmitters that are responsible for critical roles in the central nervous system, only few studies have been reported on the reliable and sensitive detection of 5-HT by the SERS technique owing to the lower Raman cross-section and lack of a common extraction method of 5-HT. In this study, a SERS-active substrate was fabricated by electrodepositing hierarchical Au nanostructures on amine-terminated ITO (indium tin oxide) glass to achieve an enhanced Raman signal of 5-HT. The electrodeposition process was performed by applying the nucleation potential E1 = 0.7 V for 2 s and the growth potential E2 = -0.2 V for 1000 s for repeated cycles. As a testing analyte, 5-HT was dissolved in four different solvents i.e. PBS buffer, Tris-HCl buffer, distilled water, and ethanol solution (20%). Among them, Tris-HCl buffer produced the most sensitive and reproducible Raman signals for 5-HT along with the lowest detection limit of ∼10-9 M due to the strong adsorption interactions between the Au surface and the indole amine groups of 5-HT under alkaline conditions. Surprisingly, the standard curve between the Raman intensity at 751 cm-1 and the log-scale concentration of 5-HT showed a linear dynamic range of over five orders of magnitude in the Tris-HCl buffer solution, suggesting a possible quantification of the 5-HT level in a biological fluid with 5-HT dysfunction or deficiency.

A novel biomimetic nanoenzyme based on ferrocene derivative polymer NPs coated with polydopamine

In this paper, ferrocene derivative polymer nanoparticles (FcP NPs) with uniform size and good photostability was synthesized using 1,1′-ferrocene dicarboxylic acid as precursor and methanol as solvent. FcP NPs-PDA was further obtained by coating of polydopamine (PDA) on FcP NPs in tris-HCl (pH=8.5) buffer solution at room temperature in the presence of dopamine (DA). The structure and morphology of FcP NPs and FcP NPs-PDA were characterized by transmission electron microscope (TEM), ultraviolet-visible spectroscopy (UV–Vis), and infrared radiation (FT-IR). The as-prepared FcP NPs-PDA showed better peroxidase-like activity than FcP NPs, which could catalyze the chromogenic reaction of peroxidase substrate TMB, OPD and ABTS. Based on the high peroxidase-like property of FcP NPs-PDA, a sensitive and convenient means to detect H2O2 has been proposed with TMB as the substrate, which displays wide linear range of 10–600 μM and 600 μM-4 mM with low detection limit of 5 μΜ. Compared with other Fe-containing NPs, such as magnetic materials and noble metal@Fe bimetallic NPs, the preparation approach for FcP NPs-PDA is simple, time and energy saving and environment friendly. This mild and simple synthesis route of FcP NPs-PDA will provide new ideas for the preparation of non-noble metal-based peroxidase-like nanomaterials and widen the applications in the fields of catalytic and analytical chemistry.

In vitro degradability and apatite-formation ability of monticellite (CaMgSiO4) bioceramic

In this study, monticellite (CaMgSiO4) ceramic was successfully synthesized by a sol–gel method. The degradation test was evaluated through the weight loss of the CaMgSiO4 ceramic during immersion in Tris–HCl buffer solution. In vitro apatite-formation ability of the CaMgSiO4 ceramic was investigated by soaking in the simulated body fluid (SBF), and the deposited hydroxyapatite (HAp) after soaking was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The results showed that the CaMgSiO4 ceramic had a low degradation rate. Furthermore, CaMgSiO4 ceramic showed good apatite-formation ability, HAp layer constituted by needle-like crystallites was investigated on CaMgSiO4 ceramic surface after soaking in SBF solution.

A novel electrochemical aptasensor based on gold electrode decorated Ag@Au core-shell nanoparticles for sulfamethazine determination

In this paper, an electrochemical aptasensor based on gold electrode (AuE)-modified Ag@Au core-shell nanoparticles was prepared. The surface of AuE was modified with Ag@Au core-shell nanoparticles to elevate APT binding sites and accelerate electron transfer properties between the electrode and ferrocene (Fc). When SM2 existed, the aptamer conformation would change and the response current intensity would increase because the Fc was pulled closer to the electrode surface. Subsequently, through a series of conditional optimization analysis, the optimal values of volume of Ag@Au core-shell, APT concentration, APT incubation time, and SM2 incubation time were 9μL, 0.2μmol/L, 75min, and 40min, respectively. Under optimum conditions, the results of differential pulse voltammetry experiments showed that the linear relationship was good in the range of 0.1~50ng/mL, ΔI' (μA) = 1.145C (ng/mL) + 54.666, R2 = 0.964, with a detection limit of 0.033ng/mL. The spiked recovery for SM2 in the pork samples was 92.6~101.0% and the relative standard deviation (RSD) was 2.7~4.1%, which indicated that the proposed aptasensor exhibited desirable performance in actual sample analysis. Graphical abstract An electrochemical aptasensor based on gold electrode-modified Ag@Au core-shell nanoparticles was prepared. The detection principle was on the basis of the change of current signal of DPV in Tris-HCl buffer solution before and after incubation of SM2. After the formation of APT-SM2 complex, the ferrocene modified on the aptamer was pulled closer to the electrode surface and sped up the electron transfer rate.

The interaction between a zinc(II) phthalocyanine compound bearing octakis phenoxyacetamide substituents and calf thymus DNA

In this study, a zinc(II) phthalocyanine compound ( PcZn ) substituted with octakis phenoxyacetamide was synthesized and characterized. Calf thymus DNA (CT-DNA) was used to determine the DNA binding properties of the zinc(II) phthalocyanine compound. This interaction of CT-DNA with PcZn was investigated using electronic absorption spectra, emission spectroscopy, a thermal melting temperature study, cyclic voltammetry, and viscosity measurements in a Tris-HCl buffer solution at a pH of 7.2. The findings showed that zinc(II) phthalocyanine interacts with calf thymus DNA via partial intercalative binding mechanisms. In addition to the techniques above, a gel electrophoresis study was also carried out to verify the interaction of CT-DNA with the PcZn complex. The results demonstrated that the octakis phenoxyacetamide-substituted zinc(II) phthalocyanine complex binds to CT-DNA via a partial intercalative binding mode.